Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.71	7.570%	$164.2701	$164.27	$164.25	$164.30
Purchase #2	$223.34	3.820%	$231.8716	$231.87	$231.85	$231.90
Purchase #3	$73.33	12.337%	$82.3767	$82.38	$82.40	$82.40
Purchase #4	$245.38	7.368%	$263.4596	$263.46	$263.45	$263.50
Purchase #5	$171.35	3.481%	$177.3147	$177.31	$177.30	$177.30
Purchase #6	$140.92	11.863%	$157.6373	$157.64	$157.65	$157.60
Purchase #7	$71.50	12.729%	$80.6012	$80.60	$80.60	$80.60
7 purchase totals =	$1,078.53		$1,157.5312	$1,157.53	$1,157.50	$1,157.60